Liquid adhesive bandages prepared from siloxy-containing hydrophobic polymers admixed with volatile liquid polydimethylsiloxanes and volatile liquid alkanes (U.S. Pat. No. 4,987,893, U.S. Pat. No. 5,103,812, the entirety of which is incorporated herein by reference, and U.S. Pat. No. 6,383,502) have been reported to provide non-stinging, non-irritating liquid bandage coating materials after solvent evaporation that allow body fluid evaporation while protecting the body surface from further contamination and desiccation. No indication of covalent crosslinking of the siloxy-containing hydrophobic polymers was taught in these patents.
Additionally, amphiphilic siloxy-containing polymers have also been reported as liquid adhesive bandages (U.S. Pat. No. 7,795,326, the entirety of which is incorporated herein by reference), wherein the hydrophobic siloxysilane monomer is copolymerized with a hydrophilic nitrogen-containing monomer.
The preferred siloxy-containing monomer for both the hydrophobic and amphiphilic liquid adhesive bandages of the above mentioned patents is based upon the siloxy monomer, 3-methacryloyloxypropyltris(trimethylsiloxy)silane (TRIS).
In U.S. Pat. No. 7,795,326, it was reported that siloxy-containing monomers may also contain low concentrations of siloxysilane crosslinking agents. These crosslinking agents could be dimeric or higher in their polymerizable groups. For example, the commercial TRIS monomer often contains minor amounts of the TRIS dimer of 1,3-bis(3-methacryloyloxypropyl)-1,1,3,3-tetrakis(trimethylsiloxy)disiloxane, which was reported to increase the strength of the coating polymer. Additionally, in U.S. Pat. No. 7,795,326 it was stated that siloxy monomer combinations containing siloxysilane crosslinking agents may be utilized provided that the resulting polymer solubility is not compromised in the volatile, hydrophobic solvent. It is taught that when the hydrophobic siloxy-containing monomer is TRIS, low concentrations of crosslinking was preferably less than 1.0 weight % of TRIS dimer, more preferably between 0.5-0.8 weight %, and most preferably between 0-0.15 weight %. Thus, in a copolymerization with other monomers, the overall dimer content in the comonomer formulation would be reduced further relative to the concentration of the added comonomers.
In general, for free radically crosslinked polymers in a compatible solvent, gelation often occurs at a crosslinking content of less than 1 weight %. In U.S. Pat. No. 3,220,960 it is taught that in copolymerization of a monomer having a polymerizable group with a small amount of a monomer having two such groups in organic solvent solution, a gel is formed by the crosslinked corresponding polymer and the solvent. Utilizing this principle, hydrogel contact lenses are reported to be made from hydrophilic esters of acrylic and methacrylic acid with a small amount of a diester of these polymerizable acids, wherein the diester preferably does not amount to more than one percent of the monomer. In such a system the original soft, 38% water, hydrogel contact lens, poly(2-hydroxyethyl methacrylate), was based upon the polymerization of the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA) crosslinked with a small amount of ethylene glycol dimethacrylate (Wichterle, O.; Lim, D., Nature, 1960, 185, 117-118), a crosslinking agent with a similar radical reactivity to that of the HEMA monomer.
Crosslinking of contact lenses with multivalent monomers is known in the contact lens industry to produce stable, insoluble materials. For example, in U.S. Pat. Nos. 7,344,731 and 7,884,141, and US Patent Application Publication Nos. 2008/0137030 and 2009/0192275, TRIS dimer has been used to produce insoluble contact lenses with a variety of other monomers. However, none of these references relates to liquid coating materials and, in direct contrast to the properties of the inventive polymers and coating materials, each of these references requires that the contact lenses are insoluble in order to maintain their function.
For pressure sensitive adhesives applied to the skin, pain usually results during dressing removal when the epidermis is damaged or when the hair is pulled by the adhesive. A strong adhesive on wounded or inflamed skin is not desired because of increased damage to the skin and a resulting delay in healing.
In the utilization of sacrificial skin coatings, adhesive failure of the coating to the skin is preferred, as opposed to the adhesive removing a portion of the epidermis, hair, or scar tissue when it is removed from the body. In the case of adhesive failure, preferably the adhesive fails at the adhesive/substrate interface, leaving little or no residue. Thus, when a stronger, more adherent pressure sensitive adhesive is applied over the sacrificial adhesive, the more tenacious adhesive removes the weaker adhesive from the skin, giving a painless (or reduced pain) removal process.
Silicone pressure sensitive adhesives and silicone gel adhesives, which are often in two part kits causing crosslinking in situ, are generally considered the most comfortable adhesives for painless removal from the skin. These are generally first applied to a backing material, crosslinked in place, and then applied to the skin. They have a disadvantage in not being applied as a liquid adhesive bandage, which limits their ability to intimately conform to a contoured skin surface or a wounded, damaged or inflamed skin surface as would a liquid adhesive bandage, which permits the polymer solution to flow into crevices and skin folds.
In US Patent Application Number 2011/0086077, highly crosslinked silicone hydrogels are discussed as tissue adhesives for wound repair, wherein silicone monomers and crosslinking agents can be applied as a wound dressing, either as a film or as an aqueous emulsion monomer solution placed upon the wound, followed by polymerization and crosslinking directly upon the wound. Such a process requires activation of polymerization, which can generate heat upon the wound when monomers polymerize. Initiation of polymerization utilizes a monomer mix containing either addition type vinyl monomers or condensation type monomers directly upon a tissue. In addition to heat being generated upon the wound or bodily surface, this is a polymerization in situ and residual monomer is often present because of incomplete polymerization. Such residual monomer upon a skin or wound surface often leads to allergic responses. Additionally, water is the preferred solvent as an oil-in-water emulsion for this polymerization, which would lead to slow drying on the skin because of the high heat of volatilization of water. Furthermore, addition of a pressure sensitive adhesive over such a formulation could be difficult if water remains in the silicone hydrogel.
Thus, there is a need in the art to provide a water-insoluble, intimately conformable, water-vapor permeable, adhesive polymer film delivered from a volatile non-stinging solvent which, after solvent evaporation, forms a polymer coating that protects the skin and wounds and acts as a sacrificial coating that can be used under strongly adherent tapes and adherent medical devices in order to reduce trauma to the underlying skin upon removal of the tape or medical device.